The A–Z of Scotch Whisky

The percentage of pure alcohol (Ethanol) in a product by its volume. By law, Scotch whisky must be bottled at a minimum strength of 40% ABV.

A Volatile compound formed during Fermentation. While present in small amounts in New make spirit, its concentration typically decreases during Maturation. In high amounts, it can contribute off-notes such as green apple, paint thinner, or cut grass.

A key component of a whisky's flavour profile, acidity adds brightness and balance. It is influenced by Fermentation and Maturation and is measured in pH. Though not often discussed, acidity plays an important role in the overall structure and Mouthfeel of whisky.

The age of the whisky refers to the number of years it has spent maturing in oak casks, from the moment it is filled into the cask until it is bottled. For all types of Scotch Whisky, the age statement must reflect the youngest whisky in the bottle.

Legally, whisky cannot be called Scotch unless it has been matured in Scotland in oak casks for a minimum of three years.

See Maturation.

Ethanol is the type of alcohol produced during fermentation and the main alcohol present in whisky. It contributes to the whisky's texture, aroma and the way flavours are perceived. Alcohol content is measured as ABV (Alcohol By Volume).

Compounds derived from the breakdown of proteins in Malted barley. During Kilning and later in Maturation, these amino acids react with sugars in Maillard reactions, contributing to the colour and flavour of whisky.

Enzymes that convert starches in malted barley into fermentable sugars during Mashing. The two primary forms are alpha-amylase and beta-amylase. Alongside limit dextrinase, they operate optimally at mashing temperatures (62–80°C) to produce sugars such as maltose and maltotriose, which are essential for Fermentation.

A 200 litre cask, typically used to mature bourbon in the United States. These Casks are commonly made from American White Oak and are widely used for maturing Scotch whisky once emptied.

Latin name: Quercus alba. Grown primarily in North America, this species is widely used in whisky cooperage due to its straight-grained wood and high levels of Vanillin. It contributes flavour notes of vanilla, coconut, honey and nuts, and is the source of most ex-bourbon casks used in Scotch Maturation.

The portion of whisky (both alcohol and water) that evaporates from the cask during Maturation. In Scotland, this loss typically ranges from 1.5–2% per year, depending on Warehouse conditions.

The scents or smells detected when Nosing whisky. Aromas arise from every stage of production - raw materials, fermentation, distillation, and maturation - and are influenced by the type of cask, length of ageing, and even warehouse conditions.

Common aromas include fruits, spices, vanilla, smoke and oak.

Nosing is a key part of whisky appreciation, as aroma contributes significantly to perceived flavour.

One of the three raw ingredients in Single malt Scotch whisky and a key ingredient in Blended Scotch whisky. Barley provides the starch that, through Mashing and Fermentation, is converted into Alcohol.

Also known as the American Standard Barrel (ASB), it is a Cask with a capacity of 200 litres (53 gallons). Widely used in the bourbon industry and commonly reused to mature Scotch whisky.

One of the five categories of Scotch whisky, blended grain whisky is a blend of single grain whiskies from more than one distillery, with no malt whisky included. It is the least common of the Scotch whisky categories.

A category of Scotch whisky made by blending single malts from different distilleries, without any grain whisky.

Formerly referred to as “Vatted Malt.”

One of the five categories of Scotch whisky defined by law, a blended whisky is a combination of one or more single malt whiskies with one or more single grain whiskies, often from multiple distilleries.

The raw materials used include water, yeast, malted barley, and other cereals such as wheat, maize, or unmalted barley.

By law, any age statement must refer to the youngest whisky in the blend.

A bonded warehouse (or bond) is a secure facility where dutiable goods, such as whisky, are stored without immediate payment of excise duty. This allows distillers to mature or bottle whisky without paying tax until it is removed for sale or export.

The ABV (alcohol by volume) at which whisky is bottled. Unless labelled as cask strength, the whisky is typically diluted with water after maturation to achieve the desired bottling strength—usually 40–46% ABV.

Casks originally used to mature bourbon, made from charred American White Oak and typically with a 200 litre capacity. Under US law, bourbon must be matured in new oak casks, so these casks are often reused in Scotch Maturation.

The first fill of bourbon removes harsher elements from the oak, leaving behind rich flavours of vanilla, coconut and caramel, which influence the whisky during its second life in Scotland.

A stopper used to seal the Bung hole in the head or belly of a cask. Usually made of wood, though modern versions may also use hard nylon.

The opening in a cask, usually located on the head or belly, through which whisky is filled or emptied. Its placement can be influenced by the warehousing style used for maturation.

A Scottish word for a stream or small river. Many distilleries take their process water from a nearby burn, which historically was considered a defining feature of whisky character.

A large cask with a capacity of approximately 500 litres. Traditionally used to mature Sherry, butts are made from European Oak and are highly prized in Scotch whisky maturation for the rich, dried fruit and spice character they can impart.

One of the five whisky regions recognised by the Scotch Whisky Association (SWA).

Located on the west coast of Scotland on the Kintyre peninsula, Campbeltown was once home to over 30 whisky distilleries in the 1800s. Today, only three remain in operation.

By law, E150a is the only permitted colouring additive in Scotch whisky. It may be added before bottling to adjust colour consistency, but not to affect flavour.

The vessel used to mature Scotch whisky. By law, casks must be made of oak and must not exceed 700 litres in capacity. Common sizes include Barrel (200 litres), Hogshead (250 litres), and Butt (500 litres).

Describes a whisky that has not been diluted with water after Maturation and is bottled at its natural strength. Also known as barrel proof.

The process of burning the inside of an oak cask to create a layer of charcoal.

There are four common levels of char:
No.1 = 15 seconds
No.2 = 30 seconds
No.3 = 35 seconds
No.4 = 55 seconds (‘alligator char’ due to its scale-like pattern)

Charring helps break down the structure of the oak, enabling greater spirit penetration and flavour extraction. The charcoal layer also acts as a natural filter, removing unwanted compounds like sulphur from the maturing spirit.

A method used to remove compounds that can cause cloudiness in whisky, especially at lower temperatures. The whisky is cooled to between –10°C and +4°C and passed through a fine filter. The process is cosmetic and does not affect flavour significantly, though opinions vary.

Climate affects the speed and nature of whisky Maturation. Warmer climates accelerate ageing and increase the Angels’ Share, while cooler climates allow for slower, gentler development.

Invented and patented by Aeneas Coffey, the continuous still (also known as the Coffey still, column still, or patent still) consists of two columns: a rectifier and an analyser. It allows for Continuous distillation and is used to produce grain spirit at a much higher ABV than malt spirit. Continuous stills can operate 24/7 and produce spirit on a larger industrial scale than pot stills.

See Coffey / Continuous Still.

A component of the distillation process that cools alcohol vapours and turns them back into liquid. Made of Copper, condensers contribute to flavour by encouraging further copper contact. Each still has its own condenser, usually one for the Wash still and one for the Spirit still. There are two types: Shell and tube, and Worm tub.

Compounds produced during Fermentation and Distillation that are responsible for much of whisky’s Aroma and flavour. Includes esters, aldehydes, acids, and higher alcohols.

Water used in the condenser system to cool alcohol vapours and return them to liquid form. The temperature and flow rate of cooling water can influence the speed of condensation and ultimately affect the character of the spirit.

A highly skilled craftsperson who builds and repairs oak Casks using traditional tools and techniques. Most distilleries rely on external cooperages, though a few still maintain their own on-site. Only four distilleries in Scotland currently have their own cooperage.

A facility where casks are manufactured, repaired and rejuvenated by Coopers. While most Scotch distilleries send their casks to large commercial cooperages, a few still maintain traditional cooperages on-site.

Copper is essential to the construction of pot stills. It is malleable, an excellent conductor of heat and chemically reactive; removing undesirable compounds such as sulphur during distillation and contributing to spirit character.

The precise moment during the spirit run when the distiller transitions from Foreshots to Heart (the spirit cut), and later from heart to Feints. Cut points are determined by the distillery based on timing, ABV, and desired style. Traditional distilleries use hydrometers and thermometers; modern ones may use automated systems.